CLI Guide

Version Description
9.10(0.1) Introduced on the S6010-ON and S4048T-ON.
9.10(0.0) Introduced on the S3148.
9.10(0.0) Introduced on the S6100–ON.
9.8(2.0) Introduced on the S3100 series.
9.8(1.0) Introduced on the Z9100–ON.
9.8(0.0P5) Introduced on the S4048-ON.
9.8(0.0P2) Introduced on the S3048-ON.
9.7(0.0) Introduced on the S6000-ON.
9.2(1.0) Introduced on the Z9500.
9.0.2.0 Introduced on the S6000.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.10.1 Introduced the loopguard and rootguard options on the S4810.
8.4.2.1 Introduced the loopguard and rootguard options on the E-Series, C-Series,
and S-Series.
8.3.7.0 Introduced on the S4810.
8.2.1.0 Introduced the shutdown-on-violation option.
7.7.1.0 Introduced on the S-Series.
7.5.1.0 Introduced on the C-Series.
6.2.1.1 Introduced on the E-Series.
Usage
Information
If you enable portfast bpduguard on an interface and the interface receives a BPDU, the software
disables the interface and sends a message stating that fact. The port is in ERR_DISABLE mode,
yet appears in the show interface commands as enabled. If you do not enable shutdown-on-
violation, BPDUs are still sent to the RPM CPU.
STP loop guard and root guard are supported on a port or port-channel enabled in any Spanning Tree
mode: Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), Multiple Spanning Tree
Protocol (MSTP), and Per-VLAN Spanning Tree Plus (PVST+).
Root guard is supported on any STP-enabled port or port-channel except when used as a stacking port.
When enabled on a port, root guard applies to all VLANs configured on the port.
STP root guard and loop guard cannot be enabled at the same time on a port. For example, if you
configure loop guard on a port on which root guard is already configured, the following error message is
displayed: % Error: RootGuard is configured. Cannot configure LoopGuard.
Do not enable Portfast BPDU guard and loop guard at the same time on a port. Enabling both features
may result in a port that remains in a blocking state and prevents traffic from flowing through it. For
example, when Portfast BPDU guard and loop guard are both configured:
● If a BPDU is received from a remote device, BPDU guard places the port in an Err-Disabled Blocking
state and no traffic is forwarded on the port.
● If no BPDU is received from a remote device, loop guard places the port in a Loop-Inconsistent
Blocking state and no traffic is forwarded on the port.
To display the type of STP guard (Portfast BPDU, root, or loop guard) enabled on a port, enter the show
spanning-tree 0 command.
Spanning Tree Protocol (STP) 1587